1. Field of the Invention
This invention relates to a fire-retardant resin composition obtained by incorporating an aromatic halogen compound in a resin composition comprising an aromatic copolyester and a polyamide.
2. Description of the Prior Art
Japanese Patent Application (OPI) Nos. 4146/75 and 98765/77 disclose a resin composition comprising (A) an aromatic copolyester, and (B) a polyamide, which has superior moldability, mechanical properties, chemical properties, electrical properties and thermal stability, and which is expected to have a very wide range of applications as electric component parts, automobile parts and machine parts. However, the fire retardancy of this resin composition is not sufficient and increasing the fire retardancy of this resin composition has been strongly desired.
Methods heretofore suggested for rendering aromatic polyesters fire-retardant include, for example, a method which comprises incorporating a halogenated organic compound, titanium phosphate and antimony oxide into aromatic polyesters (e.g., as disclosed in Japanese patent application (OPI) No. 17556/77), and a method involving adding a halogenated phenol to the polymerization system (e.g., as disclosed in Japanese Pat. No. 7470/77).
Prior techniques for rendering polyamides fire-retardant include, for example, a method which involves using both a halogenated aliphatic hydrocarbon and a phosphoric acid ester with the polyamide (e.g., as disclosed in Japanese patent application (OPI) No. 19798/77), a method involving adding melamine to the polyamide (e.g., as disclosed in Japanese Pat. No. 1994/67), a method comprising adding isocyanuric acid to the polyamide (e.g., as disclosed in Japanese Pat. No. 105744/75), and a method which comprises adding an amide-type compound to the polyamide and treating the composition with water to prevent the fire retardant from bleeding out of the composition (e.g., as disclosed in Japanese patent application (OPI) No. 16581/77).
When the above-described fire retarding compounds are added to the resin composition composed of components (A) and (B) as set forth above, the thermal stability of the composition at the time of melting is poor, and the composition decomposes during processing, for example, on extrusion or injection molding, and the superior properties of the resin composition are markedly deteriorated. Alternatively, the fire retardants bleed out with time, or the fire retardancy imparted is not sufficient. Hence, it has been necessary to discover suitable fire retardants for such a resin composition.
It is also known that an aromatic halogen compound or a mixture of an aromatic halogen compound with antimony oxide can be added to a composition comprising an aromatic polyester, a polycabonate and/or a polyalkylene terephthalate to render the composition fire retardant (e.g., as disclosed in Japanese patent application (OPI) No. 69558/76).
A resin composition comprising (A) an aromatic copolyester, (B) a polyamide, (C) a polyalkylene phenylene ester or polyalkylene phenylene ester ether, and (D) an aromatic halogen compound is disclosed in a copending U.S. patent application No. 871,168 filed Jan. 20, 1978 (corresponding to Japanese patent applications Nos. 8347/77 and 8348/77), assigned to the assignee thereof.
It has now been found that by including a suitable amount of a specific aromatic halogen compound into a resin composition comprising (A) an aromatic copolyester and (B) a polyamide, fire retardancy can be achieved.
However, in order to obtain a resin composition having a high degree of fire retardancy (for example, a fire retardancy rank of 95 V-O of UL 94 stipulated by Underwriters Laboratories, U.S.A.), quite a large amount of the aromatic halogen compound must be added to the resin composition. A resin composition which contains a large amount of the aromatic halogen compound, in comparison with a resin compound which does not contain an aromatic halogen compound, tends to be decomposed when exposed to high temperatures, e.g., during extrusion molding, injection molding, etc. Furthermore, such a resin composition tends to have inferior impact characteristics. The reason for this is not clear, but it is due presumably to an interaction between the aromatic halogen compound and the polyamide or the lack of compatibility between them.
Thus, no technique is known which can render a resin composition comprising (A) an aromatic copolyester and (B) a polyamide fire-retardant while retaining thermal stability of the resin composition during molding and dynamic characteristics, of which impact characteristics are typical.